Oil separator for compressor, scroll compressor using same, and method of manufacturing oil separator for compressor

ABSTRACT

An oil separator for a compressor according to the present invention is an oil separator (33) for separating oil flowing into a high-pressure chamber (21a) from a low-pressure chamber (21b) with a compression medium in a compressor from the compression medium, and comprises a demister (33a) which is in the form of a net formed by braiding metal thin wires and has surfaces subjected to sandblasting. Due to this structure, an oil separator for a compressor not reducing oil separability also in case of employing an HFC refrigerant and ether oil in combination with each other is implemented. The demister (33a) is formed by performing sandblasting on both front and rear surfaces of a netted strip (33a) and thereafter annularly winding the strip.

TECHNICAL FIELD

The present invention relates to an oil separator for a compressor and amethod of manufacturing the same, and more particularly, it relates toan oil separator for separating oil mixed into a refrigerant which isfed into a high-pressure chamber side in a compressor employed for arefrigerator or the like for returning the same to a low-pressurechamber side and a method of manufacturing the same.

BACKGROUND TECHNIQUE

In a compressor which is employed as an element of a refrigeration cyclefor a refrigerator, oil is supplied for the purpose of lubricating abearing part of a motor driving shaft and a compression element, andthis oil is mixed into a refrigerant in the compressor, passes throughthe compression element with the refrigerant and is discharged into ahigh-pressure chamber. When the oil thus mixed into the refrigerant isdischarged from the compressor and enters the refrigeration cycle, theheat exchange rate reduces in heat exchange in an evaporator forming therefrigeration cycle. Therefore, means for separating the oil enteringthe high-pressure chamber in the compressor from the refrigerant andreturning the same to the low-pressure chamber is adopted. An oilseparator for a compressor to which the present invention is directed isprovided as one of such means, for the purpose of separating oilentering a high-pressure chamber in the compressor from a refrigerant.

As the prior art showing this type of oil separator for a compressor, ascroll compressor on which an oil separator including a demister ismounted, disclosed in Japanese Patent Laying-Open No. 1-240787, ismentioned. The scroll compressor disclosed in this gazette connects acasing top 3 opening an outer discharge port 2 to an upper end portionof a casing body 1, and press-fits an end plate 5 of a fixed scroll 4into an opening side end portion of this casing top 3 by shrinkagefitting or the like, for forming a discharge chamber 6 which is dividedfrom the casing body 1 above the end plate 5, as shown in FIG. 6.

A frame 8 is supported for the fixed scroll 4 in opposition to a movablescroll 7, while a motor (not shown) is provided under the frame 8, sothat the movable scroll 7 is revolved/driven with respect to the fixedscroll 4 by driving of this motor. Refrigerant gas which is inhaled froma low-pressure chamber 10 is compressed between the fixed-movablescrolls 4 and 7 by this revolution/driving of the movable scroll 7, sothat this compressed refrigerant gas is discharged from a discharge hole11 provided on a central portion of the fixed scroll 4 into thedischarge chamber 6, and discharged into a discharge pipe 12 through theouter discharge port 2.

An oil separator 13 is mounted on the upper surface of the fixed scroll4 of this scroll compressor, so that the oil which is discharged intothe discharge chamber 6 with the refrigerant gas is separated from therefrigerant gas by this oil separator 13. The separated oil is returnedto the bottom side of the casing body 1 through an oil return tube 14extending in the vertical direction through the fixed scroll 4 and theframe 8. A concave part 15 is formed around the discharge chamber 6 sideend portion of the oil return tube 14, for collecting the oil separatedfrom the refrigerant gas in this concave part 15 and precipitating dustout of the oil.

The oil separator 13 is formed by a netted demister 13a which isannularly formed by winding a metal thin wire of stainless steel or thelike or a woven strip of a plurality of stranded metal thin wires aprescribed number of times, and a plate-type fitting 13b which isintegrated with the demister 13a to cover a part of its periphery andits upper surface.

As lubricating oil for a compressor for a refrigerator, SUNISO 4GS basedon mineral oil has been mainly employed since its affinity with aflon-based R22 refrigerant generally employed as a refrigerant for arefrigerator is excellent. This SUNISO 4GS is the so-called nonpolaroil, which has no polarity since no oxygen group is provided in itsmolecular structure. The nonpolar oil hardly forms monomolecular filmson the surfaces of the demister 13a of the oil separator 13, and hencethe wettability of the oil with respect to the oil separator 13 is notdamaged and the oil capturability by the oil separator 13 is excellentlymaintained.

In recent years, however, destruction of the ozone layer with theflon-based refrigerant comes into question, and there is a tendency toreplace the refrigerant with R407C, which is an HFC(Hydro-Fluoro-Carbon) refrigerant destructing no ozone layer since itcontains no chlorine, in response to the international trend ofregulating employment of the flon-based refrigerant. As lubricating oilin case of employing this HFC refrigerant, ester or ether oil which ischemosynthetic oil having excellent affinity with the HFC refrigerant isemployed. In such lubricating oil, ester or ether oil has polarity sincethe same has an oxygen group in its molecular structure. Such polar oilreadily forms monomolecular films on the surfaces of the demister 13a ofthe oil separator 13, and once monomolecular films are formed on thesurfaces of the demister 13a, the wettability of the oil with respect tothe oil separator 13 thereafter deteriorates. In other words, thesurfaces of the demister 13a provided with the monomolecular filmreadily repel the oil, and hence the oil is hardly captured by the oilseparator 13 and readily re-scattered. Consequently, the oil dischargedinto a high-pressure chamber is not separated from the refrigerant butenters the refrigeration cycle to reduce the heat exchange rate in anevaporator or the like, and hence the refrigeration efficiency isdisadvantageously reduced.

DISCLOSURE OF THE INVENTION

In order to solve the aforementioned problem of the prior art, thepresent invention is aimed at obtaining an oil separator for acompressor, whose oil separability is not reduced also when employing anHFC refrigerant and oil having polarity (e.g., ether oil) in combinationwith each other.

The inventive oil separator for a compressor according to claim 1attaining the aforementioned object is an oil separator 33 forseparating oil flowing into a high-pressure chamber 21a from alow-pressure chamber 21b with a compression medium in a compressor fromthe compression medium, which comprises a netted body part 33a formed bybraiding metal thin wires, and uneven parts for improving oilcapturability are formed on the surfaces of the metal thin wires formingthe netted body part 33a.

According to this structure, uneven parts are formed on the surfaces ofthe said metal thin wires forming the netted body part 33a, whereby thesurface area of the netted body part 33a increases and penetration ofthe oil into the uneven parts takes place, and hence the oil captureefficiency of the oil separator is increased and the oil separabilityimproves as a result.

As means for forming the uneven parts on the surfaces of the metal thinwires of the netted body part 33a of the inventive oil separator for acompressor, sandblasting is preferably applied, as described in claim 2.

Thus, the surfaces of the netted body part are treated by sandblasting,whereby the oil capture efficiency of the oil separator increases andthe oil separability can be improved. As the reasons for having actionof increasing the oil capture efficiency by treating the surfaces of thenetted body part by sandblasting, the following four items can be mainlymentioned:

(1) Uneven parts are formed on the surfaces of the netted body part,whereby the surface area increases.

(2) Small cracks are formed on the surfaces of the netted body part,thereby causing penetration of the oil.

(3) A number of lattice defects such as slip steps, rearranged ends andlattice distortion are caused on the surfaces of the netted body part,whereby the same act as energetically instable and chemical activesites, for changing the metal surfaces forming the netted body part tosurfaces which are rich in reactivity.

(4) Due to action based on an exoelectron phenomenon (Kramer's effect).The exoelectron phenomenon indicates such a phenomenon that temporaryelectron emission occurs from metal surfaces immediately after machiningsuch as blasting, which can take place under the room temperature. Theemitted exoelectrons have energy of about 1 eV, and have catalyticaction with respect to a certain type of surface reaction (these reasons(1) to (4) are described in page 222 to page 223 of "Kinzokubussei KisoKoza, Vol. 10, Kaimenbussei" issued by Maruzen Co., Ltd. on Jun. 25,1976).

In a preferred embodiment of the inventive oil separator for acompressor, the netted body part 33a includes an annular body 33a formedby winding a netted strip 33c which is formed by braiding metal thinwires once or a plurality of times, and a surface treatment for forminguneven parts for increasing the oil capturability is performed on bothfront and rear surfaces of the netted strip 33c forming the annular body33a, as described in claim 3.

Thus, uneven parts are formed on both front and rear surfaces of thenetted strip forming the annularly wound netted body part 33a, wherebythe oil comes into contact with the surfaces of the netted body part 33aa plurality of times at the time of passing through the oil separator,and hence the degree of capturing the oil increases in response to thenumber of times, and excellent oil separability can be attained.

A scroll compressor according to the present invention is a scrollcompressor formed by arranging a fixed scroll 22 provided with a spiralbody 22b on the lower surface of a substrate 22 and a movable scroll 23provided with a spiral body 23b on the lower surface of a substrate 23ato be vertically opposed to each other for combining the spiral bodies22b and 23b with each other and forming a compression chamber in aclosed housing 21 and opening a discharge hole 22c at a central portionof the substrate 22a of the fixed scroll 22 for forming a high-pressurechamber 21a above the fixed scroll 22, the high-pressure chamber 21a isprovided therein with an oil separator 33 for separating oil flowinginto the high-pressure chamber 21a from the discharge hole 22c of thefixed scroll 22 from a compression medium, the oil separator 33comprises a netted body part 33a formed by braiding metal thin wires,and uneven parts for increasing oil capturability are provided on thesurfaces of the metal thin wires forming the netted body part 33a, asdescribed in claim 4.

According to the inventive scroll compressor having such a structure,the amount of mixing of the oil into a refrigerant discharged into arefrigeration cycle can be reduced since the oil capture efficiency inthe oil separator 33 increases and the oil separability improves whenemployed as a compressor for the refrigeration cycle, whereby therefrigeration efficiency improves.

In a preferred embodiment of the inventive scroll compressor, the uppersurface of the fixed scroll 22 is arranged to divide the high-pressurechamber 21a and the low-pressure chamber 21b from each other, apartition member 30 having a discharge opening 30a communicating withthe discharge hole 22c of the fixed scroll 22 and opening in thehigh-pressure chamber 21a is provided, and the oil separator 33 is somounted on the upper surface of the partition member 30 that its nettedbody part 33a encloses the periphery of the discharge opening 30a, asdescribed in claim 5.

A method of manufacturing an oil separator for a compressor according tothe present invention comprises a step of forming a netted body 33c bybraiding a single metal thin wire or a plurality of stranded metal thinwires, a step of performing a surface treatment for forming uneven partson both front and rear surfaces of the netted body 33c, and a step ofperforming prescribed working on the surface-treated netted body 33c forforming a netted body part 33a of an oil separator 33, as described inclaim 6.

According to this manufacturing method, the inventive oil separator fora compressor having the structure described in claim 3 can be readilyformed without damaging mass producibility, and increase of theproduction cost can be suppressed to the minimum.

Preferably, the aforementioned step of performing the surface treatmentincludes a step of performing sandblasting on both front and rearsurfaces of the netted body 33c, as described in claim 7.

In a preferred embodiment of the inventive method of manufacturing anoil separator for a compressor, glass beads of not more than 200 μm ingrain size and at least 500 Hv in hardness are employed as sand in thestep of performing sandblasting, as described in claim 8.

In another preferred embodiment of the inventive method of manufacturingan oil separator for a compressor, further, the step of forming thenetted body 33c includes a step of forming a netted strip 33c, and thestep of forming the netted body part 33a includes a step of forming anannular body 33a by winding the netted strip 33c subjected to thesurface treatment once or a plurality of times, as described in claim 9.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a longitudinal section of a scrollcompressor of a type employed for a performance evaluation test of theinventive oil separator for a compressor.

FIG. 2 is a partially fragmented longitudinal sectional view showing theproximity of an oil separator provided on the scroll compressor of FIG.1 in an enlarged manner.

FIG. 3 is a partially fragmented plan view of the oil separator shown inFIG. 2.

FIG. 4A is a plan view showing an exemplary structure of a demister ofthe oil separator shown in FIGS. 1 and 2.

FIG. 4B is a sectional view taken along the line IVB--IVB in FIG. 4A.

FIG. 4C is a partially enlarged view showing a portion enclosed with acircle C in FIG. 4A in an enlarged manner.

FIG. 5A is a microphotograph showing standard wires (not sandblasted)forming a demister of an oil separator employed in an evaluation test ineach Example of an embodiment of the present invention in enlargement by75 magnifications.

FIG. 5B is a microphotograph showing a state after performingsandblasting on the surfaces of the standard wires of FIG. 5A inenlargement by 75 magnifications showing the part in enlargement.

FIG. 6 is a partially fragmented longitudinal sectional view showing thestructure of a conventional scroll compressor provided with an oilseparator.

FIG. 7 is a partially fragmented plan view of the oil separator providedon the conventional scroll compressor shown in FIG. 6.

BEST MODES FOR CARRYING OUT THE INVENTION

An embodiment of the present invention is now described with referenceto the drawings. The present invention is directed to an oil separatorfor a compressor, which is not directly influenced by the structure ofthe compressor itself, but a scroll compressor having a structureslightly different from that described with reference to theaforementioned prior art was employed in the following evaluation testin each Example of the present invention, and hence an outline of thescroll compressor which carries the oil separator for a compressoraccording to this embodiment and was employed for the evaluation test isnow described with reference to FIG. 1.

The scroll compressor shown in FIG. 1 has a structure obtained byloading an oil separator serving as an oil separator on the scrollcompressor disclosed in Japanese Patent Laying-Open No. 4-241702, forexample. This scroll compressor comprises a fixed scroll 22 and amovable scroll 23 serving as a compression part on an upper portion in aclosed casing 21. The fixed scroll 22 consists of a fixed substrate 22aand a spiral body 22b provided on its lower surface, and fixed to aframe 24 so that this spiral body 22b is directed downward. The movablescroll 23 consists of a movable substrate 23a and a spiral body 23bprovided on its upper surface, and so arranged that this spiral body 23bis opposed to the spiral body 22b of the fixed scroll 22. A bearing B isprovided on the frame 24, to support a driving shaft 25. The upperportion of this driving shaft 25 is connected to the movable scroll 23,and the lower portion is connected to a motor M.

A partition member 30 is provided above the fixed scroll 22, and ahigh-pressure chamber 21a and a low-pressure chamber 21b are formedabove and under the partition member 30 respectively. In other words,the partition member 30 serves as a divisional member dividing theinterior of the casing 21 into the high-pressure chamber 21a and thelow-pressure chamber 21b. A suction pipe 34 for introducing arefrigerant which is condensed in a condenser (not shown) to alow-temperature/low-pressure state is connected to the low-pressurechamber 21b. The refrigerant which is compressed in the compression partis discharged into the high-pressure chamber 21a through a dischargehole 22c and a concave opening 31 provided substantially at the centerof the fixed substrate 22a of the fixed scroll 22 and a dischargeopening 30a provided substantially at the center of the partition member30. A discharge pipe 32 for feeding the refrigerant which is compressedto a high-temperature/high-pressure state into an evaporator (not shown)is connected to the high-pressure chamber 21a.

A through hole 26 of a relatively large diameter is formed in the fixedscroll 22 and the frame 24. A capillary tube 28 of a small diameter isinserted in the through hole 26, and a portion close to its upper end issupported for the fixed scroll 22 by a bush 27. The lower end of thecapillary tube 28 reaches a portion close to the motor M.

An oil separator 33 is mounted on the upper surface of the partitionmember 30 of this scroll compressor, and oil discharged into thehigh-pressure chamber 21a with refrigerator gas is separated from therefrigerator gas by this oil separator 33. As shown in FIGS. 2 and 3 inan enlarged manner, the oil separator 33 is common with the oilseparator 13 in the aforementioned prior art in a point that the same isformed by a demister 33a serving as a netty body part which is annularlyformed by winding a metal thin wire of stainless steel or the like or awoven strip of a plurality of stranded metal thin wires a prescribednumber of times and a plate-type fitting 33b which is integrated withthe demister 33a to cover a part of its periphery and its upper surface,while the oil separator 33 according to this embodiment is characterizedin that the surfaces of the strip net forming the demister 33a aretreated by sandblasting, as described later.

The operation of the scroll compressor having the aforementionedstructure is now described. First, the driving shaft 25 rotates bydriving of the motor M, and the movable scroll 23 is revolved/drivenwith respect to the fixed scroll 22. The refrigerant of alow-temperature/low-pressure state introduced into the low-pressurechamber 21b from the suction pipe is introduced into a space enclosedwith the fixed scroll 22 and the movable scroll 23. The introducedrefrigerant is compressed by the revolution/driving of the movablescroll 23, and discharged into the high-pressure chamber 21a throughdischarge hole 22c, concave opening 31 and discharge opening 30a. Therefrigerant which is brought into a high-temperature/high-pressure statethereafter flows into the discharge pipe 32. Referring to FIG. 1, thickarrows show the directions of flow of the refrigerant and the oil.

Noting the flow of the oil, the oil entering the high-pressure chamber21a with the refrigerant is first separated from the refrigerant by theoil separator 33 and collected in a concave portion 29 provided in thepartition member 30, and thereafter returned to the low-pressure chamber21b through the capillary tube 28.

As hereinabove described, this embodiment employs the oil separator 33comprising the demister 33a subjected to a surface treatment bysandblasting, thereby increasing the oil capture efficiency andimproving the oil separation efficiency as compared with theconventional oil separator. A method of manufacturing this demister 33ais now described with reference to a demister having a plural number ofturns as shown in FIGS. 4A to 4C.

First, five stainless steel (e.g., SUS304) thin wires of about 0.12 mmin diameter serving as standard wires are stranded, and the same arebraided thereby forming a netted strip 33c having a prescribed lengthand a prescribed width. Thereafter this netted strip isdegreased/cleaned, and then sandblasting is performed on both front andrear surfaces. In this sandblasting, glass beads of not more than 200 μmin grain size and 500 to 550 Hv in hardness are employed as sand. In theconcrete, it is possible to employ "Blasting Beads" by ToshibaCorporation having sand components shown in the following Table 1 withgrain sizes of 150 to 200 μm. As preferable blast conditions in thesandblasting, a shot pressure of 6 kg/cm², a shot time of 1 to 2 secondsand a shot distance of about 100 mm are preferable.

FIG. 5A shows a microphotograph enlarging standard wires (notsandblasted) forming a demister of an oil separator employed for anevaluation test in each of the following Examples by 75 magnifications.FIG. 5B shows a microphotograph enlarging a state after performingsandblasting on the surfaces of the standard wires in FIG. 5A by 75magnifications.

                  TABLE 1                                                         ______________________________________                                        [Sand Components of Blasting Beads by Toshiba Corporation]                    Component  wt. %       Component wt. %                                        ______________________________________                                        SiO.sub.2  72.0        Al.sub.2 O.sub.3                                                                        1.3                                          Na.sub.2 O 14.3        K.sub.2   0.3                                          CaO         8.2        SO.sub.3  0.3                                          MgO         3.5        Others    0.1                                          ______________________________________                                    

Then, the sandblasted netted strip 33c is wound and interconnected byspot welding, whereby an annular demister 33a having a prescribed innerdiameter D₁, an outer diameter D₂ and a height H is completed as shownin FIGS. 4A to 4C, for example. A length L shown in FIG. 4C expresses awinding margin. FIGS. 4A to 4C show the case where the number of turnsis 5 and this number of turns is properly increased/decreased at need,while it can be said that the degree of separating the oil from therefrigerant increases as the number of turns increases in general, sincethe number of times at which the passing mixture of the refrigerant andthe oil comes into contact with the surfaces of the demister increases.As hereinabove described, it is possible to attain an effect bysandblasting on all surfaces through and with which the mixture of therefrigerant and the oil passes and comes into contact by performingsandblasting on both surfaces of the netted strip 33c and thereafterwinding the strip as compared with the case of performing sandblastingafter winding, and the oil separation efficiency can be improved to themaximum.

Various Examples verifying the effect by employment of the oil separator33 subjected to the surface treatment by sandblasting are described withresults of evaluation tests thereof.

EXAMPLE 1

First, an oil separability comparison test was made as Example 1, as tofive types of demister samples shown in the following Table 2, withemployment of R407C/ether oil as a combination of refrigerant/oil. Amongthe demister samples Nos. 1 to 5 shown in Table 2, No. 1 is in a basespecification consisting of wires subjected to no surface treatment, No.2 is an inventive sample subjected to sandblasting, and Nos. 3 to 5 arecomparative samples subjected to surface treatments other thansandblasting. Referring to respective Tables, demister samples providedwith * marks on the left or upper sides of the sample Nos. correspond toinventive samples, while all remaining ones are comparative sampleswhich are out of the scope of the present invention.

Results of the evaluation test are as shown in Table 2. Referring toTable 2, the oil rise rate means the weight percentage of oil in such astate that a mixture of refrigerant/oil flowing into a refrigerationcycle liquefies in a condenser, and the oil separation efficiency meansthe oil capture efficiency by a demister, i.e., (w₁ -w₂)/w₁ ×100 wt. %,assuming that w₁ represents the weight of oil flowing out in a statemixed with a refrigerant when no demister is provided, and w₂ representsthe weight of oil flowing out in a state mixed with a refrigerant when ademister is provided.

                                      TABLE 2                                     __________________________________________________________________________    [Result of Oil Separability Comparison Test by Demister Specification]        Test Conditions refrigerant/oil: R407C/ether oil                              refrigerant temperature: 55° C. on high-temperature side,              5° C. on low-temperature side                                          rotational frequency: 7500 rpm                                                                         Oil Rise                                                                 Oil Rise                                                                           Increase/Decrease                                                                       Oil Separation                             Sample              Rate Ratio to Base                                                                           Efficiency                                 No. Specification   (wt %)                                                                             Specification (%)                                                                       (%)     Manufacturability                                                                     Evaluation                 __________________________________________________________________________    1   Base  height H: 50,                                                                           1.5  --        80      ◯                                                                         --                                   number of turns: 7,                                                           outer diameter: 103,                                                          inner diameter: 86                                                  *2  Surface                                                                             sandblasting                                                                            0.5  -67       93      ◯                                                                         ⊚           3   Treatment                                                                           surface fluorine                                                                        1.0  -33       87      Δ Δ                              coating                                                             4         heat treatment                                                                          2.0  +33       73      ◯                                                                         X                                    (380° C. 30 min.)                                            5         demister winding                                                                        1.3  -13       83      ◯                                                                         Δ                              space increase                                                      __________________________________________________________________________     note 1)                                                                       *mark inventive sample, others comparative samples.                           note 2)                                                                       oil rise rate . . . weight percentage of oil in refrigerant/oil mixture       liquefied in condenser                                                        note 3)                                                                       oil separation efficiency . . . oil eapture efficiency by demister       

As understood from the test results shown in Table 2, remarkablereduction of the oil rise rate and remarkable increase of the oilseparation efficiency are implemented in case of employing the demisterof the sample No. 2 which is the inventive sample, as compared with thecase of employing the remaining demister samples of the basespecification or subjected to treatments other than sandblasting on thesurfaces. Further, the sandblasting is excellent in manufacturability ascompared with other surface treatments, and will not remarkably increasethe manufacturing cost.

EXAMPLE 2

Then, an evaluation test was carried out by rendering refrigerant/oiland other test conditions similar to the aforementioned case of Example1 and employing demister samples Nos. 6 to 8 as Example 2, for thepurpose of analyzing the effect of oil separation efficiency improvementby sandblasting in detail. Results thereof are shown in Table 3.

                                      TABLE 3                                     __________________________________________________________________________    [Evaluation Test Result (1) of Sandblasted Demister]                          Test Conditions refrigerant/oil: R407C/ether oil                              refrigerant temperature: 55° C. on high-temperature side,              5° C. on low-temperature side                                          rotational frequency: 7500 rpm                                                                        Change                                                                              Oil Rise  Oil                                                           of Oil                                                                              Increase/Decrease                                                                       Separation                            Sample                  Rise Rate                                                                           Ratio to Base                                                                           Efficiency                            No.  Specification      (wt %)                                                                              Specification (%)                                                                       (%)      Manufacturability                                                                     Evaluation           __________________________________________________________________________    *6   sandblasted (sand material: alumina)                                                             1.5→0.5                                                                      -67       93       --                                height H: 50, number of turns: 7                                              5 stranded wires                                                              outer diameter: 103,                                                          inner diameter: 86, 119 g                                                *7-1 sandblasted (sand material: glass beads)                                                         2.6→0.5                                                                      -81       93       ◯                                                                         ⊚     *7-2 height H: 50, number of turns: 7                                                                 2.0→0.4                                                                      -80       94                                         5 stranded wires                                                              outer diameter: 103,                                                          inner diameter: 86, 119 g                                                 8   not sandblasted    1.5→0.9                                                                      -40       88       ◯                                                                         ◯             press-formed product                                                          height H: 52, number of turns: 7                                              1 stranded wire                                                               outer diameter: 103,                                                          inner diameter: 86, 119 g                                                __________________________________________________________________________     note 1)                                                                       *marks inventive samples, the rest comparative sample.                        note 2)                                                                       oil rise . . . weight percentage of oil in refrigerant/oil mixture            liquefied in condenser (e.g., "1.5→0.5" means that an oil rise rat     which had been 1.5 wt. % in the base specification became 0.5 wt. % in th     demister)                                                                     note 3)                                                                       oil separation efficiency . . . oil capture efficiency by demister       

As described on the column of "specification" in Table 3, the sample No.6 and the samples Nos. 7-1 and 7-2 are inventive samples subjected tosandblasting, while the sample No. 8 is a comparative sample subjectedto no sandblasting but press-formed. As understood from the evaluationtest results shown in Table 3, the oil separation efficiency increasesin case of employing the inventive samples subjected to sandblasting, ascompared with the case of employing the comparative sample (sample No.8) subjected to no sandblasting.

EXAMPLE 3

Then, an evaluation test was carried out by changing the capacity of acompressor serving as a base and employing demister samples No. 9(inventive sample) and Nos. 10-1 and 10-2 (comparative samples) shown inTable 4 as Example 3, for a purpose similar to the aforementionedExample 2. Following the change of the capacity of the compressor, thesizes of the demisters carried thereon are also changed in this case.Also from the test results shown in Table 4, it is understood that theoil rise rate remarkably reduces in case of employing the demister ofthe sample No. 9 which is the inventive sample as compared with thecomparative samples.

                  TABLE 4                                                         ______________________________________                                        [Evaluation Test Result (2) of Sandblasted Demister]                          Test Conditions                                                               refrigerant/oil: R407C/ether oil                                              refrigerant temperature: 55° C. on high-temperature side,              5° C. on low-temperature side                                          rotational frequency: 3600 rpm                                                                                Oil Rise Increase/                                                 Change of  Decrease Ratio to                             Sample               Oil Rise Rate                                                                            Base Specification                            No.   Specification  (wt %)     (%)                                           ______________________________________                                        *9    sandblasted    1.3 → 0.24                                                                        -82                                                 height H: 42,                                                                 number of turns: 7                                                            5 stranded wires                                                              outer diameter: 113,                                                          inner diameter: 96, 104 g                                               10-1  not sandblasted                                                                              1.3 → 0.6                                                                         -51                                                 press-formed product                                                          height H: 42                                                            10-2  1 stranded wire                                                                              1.5 → 0.4                                                                         -73                                                 outer diameter: 113,                                                          inner diameter: 96, 103 g                                               ______________________________________                                         note 1) *mark inventive sample, others comparative samples.                   note 2) oil rise rate . . . weight percentage of oil in refrigerant/oil       mixture liquefied in condenser (e.g., "1.3 → 0.24" means that an       oil rise rate which had been 1.3 wt. % in the base specification became       0.24 wt. % in the demister)                                              

EXAMPLE 4

Then, an evaluation test was carried out by employing demister samplesNo. 11 (inventive sample) and No. 12 (comparative sample) shown in Table5 as Example 4, for a purpose similar to the aforementioned Examples 2and 3. Also from the test results shown in Table 5, it is understoodthat the oil rise rate remarkably reduces in case of employing thedemister of the sample No. 11 which is the inventive sample as comparedwith the comparative sample.

                  TABLE 5                                                         ______________________________________                                        [Evaluation Test Result (3) of Sandblasted Demister]                          Test Conditions                                                               refrigerant/oil: R407C/ether oil                                              refrigerant temperature: 55° C. on high-temperature side,              5° C. on low-temperature side                                          rotational frequency: 3600 rpm                                                                                Oil Rise Increase/                                                 Change of  Decrease Ratio to                             Sample               Oil Rise Rate                                                                            Base Specification                            No.   Specification  (wt %)     (%)                                           ______________________________________                                        11    sandblasted    1.4 → 0.4                                                                         -71                                                 height H: 42,                                                                 number of turns: 7                                                            5 stranded wires                                                              outer diameter: 129,                                                          inner diameter: 112,                                                          120 g                                                                   12    not sandblasted                                                                              1.4 → 0.8                                                                         -43                                                 press-formed product                                                          height H: 42                                                                  1 stranded wire                                                               outer diameter: 129,                                                          inner diameter: 112,                                                          118 g                                                                   ______________________________________                                         note 1) *mark inventive sample, the other comparative sample.                 note 2) oil rise rate . . . weight percentage of oil in refrigerant/oil       mixture liquefied in condenser (e.g., "1.4 → 0.4" indicates that a     oil rise rate which had been 1.4 wt. % in the base specification became       0.4 wt. % in the demister)                                               

EXAMPLE 5

Then, a test of evaluating oil separability as to two types ofR22/SUNISO 4GS and R407C/ether oil as combinations of refrigerant/oilwas carried out as Example 5 under test conditions shown in Table 6. Asdemisters directed to a test for comparison, a sample No. 13(comparative sample) of the base specification with no surfacetreatment, a sample No. 14 (inventive sample) subjected to sandblasting,and a sample No. 15 (comparative sample) subjected to no sandblastingbut press-formed described on the column of the specification in Table 6were employed.

                                      TABLE 6                                     __________________________________________________________________________    [Result of Oil Separability Comparison Test by Two Types of                   Refrigerant/Oil]                                                              Test Conditions refrigerant temperature: 55° C. on                     high-temperature side, 5° C. on low-temperature side                   rotational frequency: 7500 rpm                                                                    R22/SUNISO 4GS        R407C/ether oil                                         Oil  Oil Rise  Oil    Oil Oil Rise   Oil                  Refrigerant/Oil     Rise Increase/Decrease                                                                       Separation                                                                           Rise                                                                              Increase/Decrease                                                                        Separation           Sample              Rate Ratio to Base                                                                           Efficiency                                                                           Rate                                                                              Ratio to Base                                                                            Efficiency           No.  Specification  (wt %)                                                                             Specification (%)                                                                       (%)    (wt %)                                                                            Specification                                                                            (%)                  __________________________________________________________________________    13   Base                                                                             height H: 50,                                                                             0.8  --        92     1.5 --         80                           number of turns: 7                                                            outer diameter: 103,                                                          inner diameter: 85, 119 g                                             *14  sandblasted    0.3  -63       97     0.4 -73        95                        height H: 50, number of turns: 7,                                             7 stranded wires                                                              outer diameter: 103,                                                          inner diameter: 86, 119 g                                                15   not sandblasted                                                                              0.6  -25       94     0.9 -40        88                        height H: 52,                                                                 1 stranded wire                                                               press-formed product                                                          outer diameter: 129,                                                          inner diamter 86, 119 g                                                  __________________________________________________________________________     note 1)                                                                       *mark inventive sample, others comparative samples.                           note 2)                                                                       oil rise . . . weight percentage of oil in refrigerant/oil mixture            liquefied in condenser                                                        note 3)                                                                       oil separation efficiency . . . oil capture efficiency by demister       

From the test results of Table 6, it is understood that excellent oilseparability can be attained in either one of the two types ofrefrigerant/oil combinations. Namely, the inventive sample subjected tosandblasting also has such an advantage that the same is applicable tothe two types of refrigerants/oil combinations in common, and the effectis particularly eminent when an oil having polarity is used (see to thedata of R407C/ether oil in Table 6).

While sandblasting has been employed as the surface treatment means forforming uneven parts on the surfaces of the metal thin wires forming thenetted strip 33c of the demister in the aforementioned each embodiment,it is needless to say that employment of another treatment means bywhich concave parts increasing the oil capture efficiency are formed onthe surfaces of the metal thin wires is possible.

Further, the aforementioned embodiment disclosed this time is a mereillustration, the scope of the present invention is shown by the scopeof claim for patent, and it is intended that all inner changes areincluded in supremacy equal to the description of the scope of claim forpatent.

What is claimed is:
 1. An oil separator for a compressor for separatingoil flowing into a high-pressure chamber from a low-pressure chamberwith a compression medium in a compressor from the compressionmedium,comprising a netted body part being formed by braiding a metalthin wire, said netted body part including uneven parts for increasingoil capturability which are formed on the surfaces of said metal thinwire forming said netted body part.
 2. The oil separator for acompressor in accordance with claim 1, wherein the uneven parts on thesurfaces of said metal thin wire forming said netted body part areformed by sandblasting.
 3. The oil separator for a compressor inaccordance with claim 1, wherein said netted body part includes anannular body being formed by winding a netted strip formed by braidingthe metal thin wire once or a plurality of times, and a surfacetreatment for forming the uneven parts for increasing oil capturabilityis performed on both front and rear surfaces of said netted stripforming said annular body.
 4. A scroll compressor being formed byarranging a fixed scroll provided with a spiral body on the lowersurface of a substrate and a movable scroll provided with a spiral bodyon the lower surface of a substrate to be vertically opposed to eachother for combining said spiral bodies with each other and forming acompression chamber in a closed housing and opening a discharge hole ata central portion of said substrate of said fixed scroll for forming ahigh-pressure chamber above said fixed scroll, whereinsaid high-pressurechamber is provided therein with an oil separator for separating oilflowing into said high-pressure chamber from the discharge hole of saidfixed scroll from a compression medium, and said oil separator comprisesa netted body part formed by braiding a metal thin wire, said nettedbody part having uneven parts for increasing oil capturability on thesurfaces of said metal thin wire forming said netted body part.
 5. Thescroll compressor in accordance with claim 4, wherein a partition memberbeing arranged to division said high-pressure chamber and thelow-pressure chamber from each other and having a discharge openingcommunicating with said discharge hole of said fixed scroll and openingin said high-pressure chamber is provided on the upper surface of saidfixed scroll, andsaid oil separator is mounted on the upper surface ofsaid partition member so that said netted body part thereof encloses theperiphery of said discharge opening.
 6. A method of manufacturing an oilseparator for a compressor, comprising:forming a netted body by braidinga metal thin wire or a plurality of stranded metal thin wires;performing a surface treatment for forming uneven parts on both frontand rear surfaces of said netted body; and performing prescribed workingon said netted body being subjected to said surface treatment, forforming a netted body part of an oil separator.
 7. The method ofmanufacturing an oil separator for a compressor in accordance with claim6, wherein said step of performing said surface treatment includes astep of performing sandblasting on both front and rear surfaces of saidnetted body.
 8. The method of manufacturing an oil separator for acompressor in accordance with claim 7, wherein glass beads of not morethan 200 μm in grain size and at least 500 Hv in hardness are employedas sand in said step of performing said sandblasting.
 9. The method ofmanufacturing an oil separator for a compressor in accordance with claim7, wherein said step of forming said netted body includes a step offorming a netted strip, andsaid step of forming said netted body partincludes a step of forming an annular body by winding said netted stripbeing subjected to said surface treatment once or a plurality of times.10. The oil separator for a compressor in accordance with claim 1,wherein small cracks are formed on surfaces of said netted body parts,thereby causing penetration of the oil.
 11. The oil separator for acompressor in accordance with claim 1, wherein a number of latticedefects are formed on surfaces of said netted body parts.
 12. The oilseparator for a compressor in accordance with claim 4, wherein smallcracks are formed on surfaces of said netted body parts, thereby causingpenetration of the oil.
 13. The oil separator for a compressor inaccordance with claim 4, wherein a number of lattice defects are formedon surfaces of said netted body parts.